Five-layered, biaxially-oriented, sealable tubular film for the packaging and wrapping of paste-like foodstuffs meat and meat with bones and use thereof

ABSTRACT

The invention relates to a five-layered, biaxially oriented, shrinkable, sealable tubular film for the packaging and wrapping of paste-like foodstuffs, meat, or meat with bones and to the use thereof. The tubular film of the invention has an inner layer comprised of at least one copolyamide and at least one modified polyolefin, a layer of a modified polyolefin, a middle layer comprised of at least one homopolyamide and/or at lest one copolyamide and/or at least one copolymer of ethylene and vinyl alcohol and/or a modified polyolefin, a layer of at least one ethylene-vinyl alcohol copolymer, and an outer layer comprised of at least one polyolefin and/or at least one modified polyolefin. Such tubular films involve a significant improvement in the seal seam strength, in particular at low sealing temperatures, a high impermeability to oxygen and a comparable to markedly higher resistance to puncturing compared to prior art films.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The invention relates to a five-layered, biaxially oriented, shrinkable,sealable tubular film with improved oxygen barrier and to its use forthe packaging and wrapping of paste-like foodstuffs, meat, and meat withbones.

2. Description of the Background

A five-layered, polyamide-based tubular film for packaging and wrappingpasty foodstuffs, especially a sausage skin, is already known from DE 4339 337 C2. This tubular film is comprised of an inner layer and an outerlayer made of the same polyamide material, a middle polyolefin layer andtwo adhesion-promoting layers made of the same material and situatedbetween the inner layer and middle layer and between the middle layerand outer layer. The inner and outer layers consist of at least onealiphatic polyamide and/or at least one aliphatic copolyamide and atleast one partially aromatic polyamide and/or at least one partiallyaromatic copolyamide, the amount of partially aromatic polyamide and/orcopolyamide being from 5 to 60 wt.-%, relative to the total weight ofthe polymer mixture of partially aromatic and aliphatic polyamides andcopolyamides. Such a tubular film, produced by coextrusion, is providedwith controlled shrinkability by biaxial stretching and heat-setting.With respect to its technological properties important to wrapping andpackaging of meat, especially meat with bones, such a tubular filmrequires some improvements. In the event of meat with bones there is arisk of protruding bones piercing the packaging film following shrinkingof the packaging film on the packaged item, because the punctureresistance is insufficient. Furthermore, such tubular films forpackaging and wrapping meat or meat with bones and pasty foodstuffsshould also allow sealing by simple heat-sealing. With bags producedusing such tubular films, the strength of the seal seam is a crucialissue. For example, when a piece of ham or meat drops out of a spout andinto a bag made of a plastic film and sealed at its bottom by aheat-seal seam, considerable loads—depending on the weight—arise due tothe product to be packaged dropping into the bag, possibly giving riseto tearing of the heat-seal seam and complete opening of the bag at thebottom thereof. Also, the heat-seal seam is exposed to extreme loadduring subsequent vacuum treatment and shrinking of the bags. Likewise,shipment and storage of the filled bags involve high demands on thepuncture resistance of the film and on the seal seam strength.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to provide a biaxiallyoriented, shrinkable, sealable tubular film for the packaging andwrapping of pasty foodstuffs, meat, and meat with bones which, inaddition to the requirements to be met by such a packaging film, such aslow water vapor and oxygen permeabilities, firstly has high punctureresistance of the tubular film and secondly high strength of the sealseam.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Another object of the invention is to further improve the packaging filmwith respect to its impermeability to oxygen.

According to the invention, said object is accomplished by means of afive-layered, biaxially oriented, shrinkable, sealable tubular filmhaving the characterizing features of claim 1.

The inner layer includes at least one sealable copolyamide. These per seknown copolyamides are produced from monomers selected from the group ofcaprolactam, laurinlactam, ω-aminoundecanoic acid, adipic acid, azelaicacid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid,terephthalic acid, isophthalic acid, tetramethylenediamine,pentamethylenediamine, hexamethylenediamine, octamethylenediamine, andxylylenediamine. The wall thickness of the inner layer is between 5 and16 μm.

Surprisingly, addition of an amorphous polyamide and/or of ahomopolyamide and/or of a modified polyolefin to a copolyamide in theinner layer significantly increases the strength of the seal seamcompared to pure copolyamide, and high seal seam strength is achievedeven at low sealing temperatures. Consequently, the film of theinvention presents considerable technological advantages.

Polyamides having a glass transition temperature between 50 and 200° C.in dry state are used as amorphous polyamides for the inner layer.Examples are polyamide 6I/6T, polyamide 6-3-T and polyamide 6I.

Polyamides which can be produced from the same monomers as thecopolyamides described above are used as homopolyamides for the innerlayer. The homopolyamides can be both aliphatic and partially aromaticin character.

The modified polyolefins are copolymers of ethylene or propylene andoptionally other linear α-olefins having from 3 to 8 C atoms andα,β-unsaturated carboxylic acids, preferably acrylic acid, methacrylicacid and/or metal salts and/or alkyl esters thereof, or appropriategraft copolymers of the above-mentioned monomers on polyolefins, orpartially saponified ethylene-vinyl acetate copolymers which areoptionally graft-polymerized with an α,β-unsaturated carboxylic acid andhave a low saponification level, or mixtures thereof. Furthermore, themodified polyolefins can be modified homo- or copolymers of ethyleneand/or propylene and optionally other linear α-olefins having from 3 to8 C atoms, which have monomers from the group of α,β-unsaturateddicarboxylic acids, preferably maleic acid, fumaric acid, itaconic acid,or anhydrides, esters, amides or imides thereof grafted thereon.

The major component of the inner layer is a sealable copolyamide or amixture of sealable copolyamides, said major component being present inamounts of between 50 and 95 wt.-%. Each of the other components,amorphous polyamide and/or homopolyamide and/or modified polyolefin, canbe admixed to the major component in amounts of from 1 to 30 wt.-%,preferably from 5 to 25 wt.-%, relative to the overall inner layer.

The layer of modified polyolefin is comprised of copolymers of ethyleneor propylene and optionally other linear α-olefins having from 3 to 8 Catoms and α,β-unsaturated carboxylic acids, preferably acrylic acid,methacrylic acid and/or metal salts and/or alkyl esters thereof, orappropriate graft copolymers of the above-mentioned monomers onpolyolefins, or partially saponified ethylene-vinyl acetate copolymerswhich are optionally graft-polymerized with an α,β-unsaturatedcarboxylic acid and have a low saponification level, or mixturesthereof. Furthermore, the modified polyolefins can be modified homo- orcopolymers of ethylene and/or propylene and optionally other linearα-olefins having from 3 to 8 C atoms, which have monomers from the groupof α,β-unsaturated dicarboxylic acids, preferably maleic acid, fumaricacid, itaconic acid, or anhydrides, esters, amides or imides thereofgrafted thereon. The wall thickness of the modified polyolefin layer isbetween 5 and 30 μm.

In addition, the oxygen impermeability of the film is dramaticallyimproved by an oxygen barrier layer comprised of an ethylene-vinylalcohol copolymer, situated between the outer layer and middle layer,and by using a polyamidebased middle layer.

A layer comprised of at least one homopolyamide and/or at least onecopolyamide and/or at least one copolymer of ethylene and vinyl alcoholand/or a modified polyolefin is used as middle layer in the wrappingaccording to the invention. The wall thickness wall of this layer isbetween 10 and 35 μm.

Suitable homo- and copolyamides are well-known and can be produced fromthe corresponding monomers such as caprolactam, laurinlactam,ω-aminoundecanoic acid, adipic acid, azelaic acid, sebacic acid,decanedicarboxylic acid, dodecanedicarboxylic acid, terephthalic acid,isophthalic acid, tetramethylenediamine, pentamethylenediamine,hexamethylenediamine, octamethylenediamine, and xylylenediamine.

Preferred homo- and copolyamides are polyamide 6, polyamide 12,polyamide 610, polyamide 612, polyamide MXD6, polyamide 6/66, polyamide6/12, polyamide 6I/6T.

The modified polyolefins which can be included in the middle layer arecopolymers of ethylene or propylene and optionally other linearα-olefins having from 3 to 8 C atoms and α,β-unsaturated carboxylicacids, preferably acrylic acid, methacrylic acid and/or metal saltsand/or alkyl esters thereof, or appropriate graft copolymers of theabove-mentioned monomers on polyolefins, or partially saponifiedethylene-vinyl acetate copolymers which are optionally graft-polymerizedwith an α,β-unsaturated carboxylic acid and have a low saponificationlevel, or mixtures thereof. Furthermore, the modified polyolefins can bemodified homo- or copolymers of ethylene and/or propylene and optionallyother linear α-olefins having from 3 to 8 C atoms, which have monomersfrom the group of α,β-unsaturated dicarboxylic acids, preferably maleicacid, fumaric acid, ylic acids, preferably maleic acid, fumaric acid,itaconic acid, or anhydrides, esters, amides or imides thereof graftedthereon.

The copolymers of ethylene and vinyl alcohol which can be included inthe middle layer are produced by complete saponification of copolymersof ethylene and vinyl acetate. In general, the amount of ethylene in theethylene-vinyl alcohol copolymers is between 27 and 48 mole-%. Foraddition to the middle layer, ethylene-vinyl alcohol copolymers arepreferred wherein the amount of ethylene is between 27 and 38 mole-%.

The major component of the middle layer is comprised of homopolyamides,alone or in mixture, copolyamides, alone or in mixture, or of mixturesof homo- and copolyamides, said major component being present in amountsof between 50 and 100 wt.-%. Where additional components such ascopolymers of ethylene and vinyl alcohol and/or modified polyolefins arepresent, each one is admixed to the major component in amounts of from 0to 50 wt.-%, relative to the overall middle layer.

Next, a layer of an ethylene-vinyl alcohol copolymer is provided,comprised of the same copolymers which can be included in the middlelayer, but in this case, the preferred amount of ethylene is between 34and 48 mole-%. The ethylene-vinyl alcohol copolymers of this layer canbe added with homo- or copolyamides and/or modified polyethylenes. Thewall thickness of this layer is between 3 and 10 μm.

Suitable homo- and copolyamides are well-known and can be produced fromthe corresponding monomers such as caprolactam, laurinlactam,ω-aminoundecanoic acid, adipic acid, azelaic acid, sebacic acid,decanedicarboxylic acid, dodecanedicarboxylic acid, terephthalic acid,isophthalic acid, tetramethylenediamine, pentamethylenediamine,hexamethylenediamine, octamethylenediamine, and xylylenediamine.

Preferred homo- and copolyamides are polyamide 6, polyamide 12,polyamide 610, polyamide 612, polyamide MXD6, polyamide 6/66, polyamide6/12, polyamide 6I/6T.

The modified polyolefins are copolymers of ethylene or propylene andoptionally other linear α-olefins having from 3 to 8 C atoms andα,β-unsaturated carboxylic acids, preferably acrylic acid, methacrylicacid and/or metal salts and/or alkyl esters thereof, or appropriategraft copolymers of the above-mentioned monomers on polyolefins, orpartially saponified ethylene-vinyl acetate copolymers which areoptionally graft-polymerized with an α,β-unsaturated carboxylic acid andhave a low saponification level, or mixtures thereof. Furthermore, themodified polyolefins can be modified homo- or copolymers of ethyleneand/or propylene and optionally other linear α-olefins having from 3 to8 C atoms, which have monomers from the group of α,β-unsaturateddicarboxylic acids, preferably maleic acid, fumaric acid, itaconic acid,or anhydrides, esters, amides or imides thereof grafted thereon.

The major component of this layer is an ethylene-vinyl alcohol copolymerin an amount of from 60 to 100 wt.-%. Where additional components suchas homo- and copolyamides and modified polyolefins are present, each onebe admixed to the major component in amounts of from 0 to 40 wt.-%,relative to the overall layer.

The outer layer consists of polyolefins or of modified polyolefins.Arbitrary mixtures of these components can also be used as outer layer.The wall thickness of this layer is between 3 and 15 μm.

Homopolymers of ethylene or propylene and/or copolymers of linearα-olefins having from 2 to 8 C atoms are preferably used as polyolefins.Linear low-density polyethylene, high-density polyethylene,polypropylene homopolymer, polypropylene block copolymer andpolypropylene random copolymer are preferably used for the middle layer.

The modified polyolefins are copolymers of ethylene or propylene andoptionally other linear α-olefins having from 3 to 8 C atoms andα,β-unsaturated carboxylic acids, preferably acrylic acid, methacrylicacid and/or metal salts and/or alkyl esters thereof, or appropriategraft copolymers of the above-mentioned monomers on polyolefins, orpartially saponified ethylene-vinyl acetate copolymers which areoptionally graft-polymerized with an α,β-unsaturated carboxylic acid andhave a low saponification level, or mixtures thereof. Furthermore, themodified polyolefins can be modified homo- or copolymers of ethyleneand/or propylene and optionally other linear α-olefins having from 3 to8 C atoms, which have monomers from the group of α,β-unsaturateddicarboxylic acids, preferably maleic acid, fumaric acid, itaconic acid,or anhydrides, esters, amides or imides thereof grafted thereon.

In addition, conventional auxiliary agents such as anti-blocking agents,stabilizers, antistatic agents or lubricants can be included in thetubular film. These auxiliary agents are normally added in amounts offrom 0.1 to 5 wt.-%. Furthermore, the film can be colored by addingpigments or pigment mixtures.

The tubular films of the invention are produced by coextrusion whereinthe individual polymers for the separate layers are plastified andhomogenized in five extruders, and the five melt streams, according tothe desired single wall thickness ratios, are subsequently extrudedthrough a five-layer extrusion head to form a primary tube and subjectedto biaxial stretching and heat-setting.

The tubular films of the invention have an overall wall thickness offrom 30 to 100 μm, preferably from 40 to 80 μm.

Surprisingly, the tubular films of the invention are clearly superior tothe tubular films of DE 43 39 337 C2 with respect to seal seam strength,puncture resistance and oxygen permeability.

To determine the seal seam strength, each tubular film was welded insideat a right angle to the machine direction, using an SGPE 20 laboratorywelding apparatus from W. Kopp Verpackungsmaschinen. Strips 25 mm inwidth were taken from the welded tubular films in such a way that thewelding seam was at a right angle to the length of the strip. The stripsamples were stretched on a tensile testing machine from Instron Companyat a stretching rate of 500 mm/min until breaking of the weld seamoccurred. The resulting maximum force will be referred to as seal seamstrength hereinafter.

As a measure for the puncture resistance, the damaging energy isdetermined in a penetration test.

The damaging energy was determined following DIN 53373, but deviatingfrom said DIN standard, a hardened cylindrical form A pin 3 mm indiameter, according to DIN EN 28 734, was used as impact body and thetesting rate was 500 mm/min. The damaging energy is the energy that isabsorbed until initial tearing of the sample occurs.

The oxygen permeability was determined according to ASTM D3985-81(88) at23° C. and 50% relative humidity, using an OXTRAN 200-H from ModernControls Inc.

The tubular film according to DE 43 39 337 C2 (Comparative Example 1)could not be welded at sealing temperatures of 140 and 200° C., whilethe tubular films of the invention achieved satisfactory to good sealseam strength already at a sealing temperature of 140° C. At a sealingtemperature of 200° C., the tubular films of the invention exhibit sealseam strengths which are at least 18% higher than those of theComparative Examples.

The tubular films according to the invention exhibit comparable tosignificantly higher damaging energy values in the penetration test aswell.

The invention will be illustrated in more detail with reference to thefollowing examples.

EXAMPLE 1

The individual polymers for the separate layers were plastified andhomogenized in five extruders. According to the desired single wallthickness ratios, the five melt streams were fed into a five-layerextrusion head, formed into a primary tube and subjected to biaxialstretching and heat-setting. The primary tube had a diameter of 45.5 mmand a mean overall wall thickness of 0.50 mm. It was heated to 116° C.using infrared radiation and stretched at a surface stretch ratio of9.2. The biaxially stretched tube was heat-set, flattened, and wound up.The mean overall wall thickness of the tube was 55 μm, and the flatwidth was 210 mm.

The layers of the final tube consisted of the following polymers, with asingle wall thickness as indicated:

1^(st) layer (outer Blend of 40% polyethylene (LDPE), Lupolen 1804Hlayer): from BASF AG and 60% modified polyethylene, Admer NF 478 E fromMitsui Chemicals Inc., 6 μm 2^(nd) layer: Ethylene-vinyl alcoholcopolymer, Soarnol AT4406 from Nippon Gohsei, 6 μm 3^(rd) layer:Polyamide 6/12, Grilon CR9 from EMS Chemie, 22 μm 4^(th) layer: Adhesionpromotor, modified polyethylene, Admer NF 478 E from Mitsui ChemicalsInc., 11 μm 5^(th) layer (inner Blend of 90% polyamide 6/12, Grilon CF6Sfrom EMS layer): Chemie and 10% polyamide 12, UBE Nylon 3030 B from UBEIndustries Ltd., 10 μm

The following seal seam strength values were determined:

Sealing temperature 140° C.:  8 N/25 mm Sealing temperature 200° C.: 94N/25 mm

The damaging energy was 560 mJ.

The oxygen permeability was 6.0 cm³/m² dbars.

EXAMPLE 2

The individual polymers for the separate layers were plastified andhomogenized in five extruders. According to the desired single wallthickness ratios, the five melt streams were fed into a five-layerextrusion head, formed into a primary tube and subjected to biaxialstretching and heat-setting. The primary tube had a diameter of 45.5 mmand a mean overall wall thickness of 0.53 mm. It was heated to 108° C.using infrared radiation and stretched at a surface stretch ratio of9.7. The biaxially stretched tube was heat-set, flattened, and wound up.The mean overall wall thickness of the tube was 55 μm, and the flatwidth was 208 mm.

The layers of the final tube consisted of the following polymers, with asingle wall thickness as indicated:

1^(st) layer (outer Blend of 40% polyethylene (LDPE), Lupolen 1804Hlayer): from BASF AG and 60% modified polyethylene, Admer NF 478 E fromMitsui Chemicals Inc., 6 μm 2^(nd) layer: Ethylene-vinyl alcoholcopolymer, Soarnol AT4406 from Nippon Gohsei, 6 μm 3^(rd) layer: Blendof 40% polyamide 6, Grilon F40 from EMS Chemie and 50% polyamide 6/66,Ultramid C35 from BASF AG, and 10% polyamide 6I/6T, Grivory G21 from EMSChemie, 21 μm 4^(th) layer: Adhesion promotor, modified polyethylene,Admer NF 478 E from Mitsui Chemicals Inc., 12 μm 5^(th) layer (innerBlend of 90% polyamide 6/12, Grilon CF6S from EMS layer): Chemie and 10%ionomer resin, Surlyn 1652 from Du Pont de Nemours GmbH, 10 μm

The following seal seam strength values were determined:

Sealing temperature 140° C.: 73 N/25 mm Sealing temperature 200° C.: 94N/25 mm

The damaging energy was 585 mJ.

The oxygen permeability was 5.2 cm³/m² dbars.

EXAMPLE 3

The individual polymers for the separate layers were plastified andhomogenized in five extruders. According to the desired single wallthickness ratios, the five melt streams were fed into a five-layerextrusion head, formed into a primary tube and subjected to biaxialstretching and heat-setting. The primary tube had a diameter of 45.5 mmand a mean overall wall thickness of 0.52 mm. It was heated to 115° C.using infrared radiation and stretched at a surface stretch ratio of9.4. The biaxially stretched tube was heat-set, flattened, and wound up.The mean overall wall thickness of the tube was 55 μm, and the flatwidth was 211 mm.

The layers of the final tube consisted of the following polymers, with asingle wall thickness as indicated:

1^(st) layer (outer Blend of 40% polyethylene (LDPE), Lupolen 1804Hlayer): from BASF AG and 60% modified polyethylene, Admer NF 478 E fromMitsui Chemicals Inc., 6 μm 2^(nd) layer: Ethylene-vinyl alcoholcopolymer, Soarnol AT4406 from Nippon Gohsei, 6 μm 3^(rd) layer:Polyamide 6, Grilon F40 from EMS Chemie, 21 μm 4^(th) layer: Adhesionpromotor, modified polyethylene, Admer NF 478 E from Mitsui ChemicalsInc., 12 μm 5^(th) layer (inner Blend of 85% polyamide 6/12, Grilon CF6Sfrom EMS layer): Chemie and 5% polyamide 6I/6T, Grivory G21 from EMSChemie and 10% ionomer resin, Surlyn 1652 from Du Pont de Nemours GmbH,10 μm

The following seal seam strength values were determined:

Sealing temperature 140° C.: 13 N/25 mm Sealing temperature 200° C.: 97N/25 mm

The damaging energy was 530 mJ.

The oxygen permeability was 6.1 cm³/m² dbars.

COMPARATIVE EXAMPLE 1

A five-layered tubular film with the following structure was producedaccording to DE 43 39 337 C2:

1^(st) layer (outer Blend of 95% polyamide 6, Durethan B40 F from Bayerlayer): AG and 5% polyamide 6I/6T, Grivory G21 from EMS Chemie, 21 μm2^(nd) layer: Adhesion promotor, modified polyethylene, Admer NF 478 Efrom Mitsui Chemicals Inc., 5 μm 3^(rd) layer: Polyethylene (LLDPE),Dowlex 2049 E from DOW Chemical Company, 15 μm 4^(th) layer: Adhesionpromotor (as in layer 2), 5 μm 5^(th) layer (inner Blend of 95%polyamide 6, Durethan B40 F from Bayer layer): AG and 5% polyamide6I/6T, Grivory G21 from EMS Chemie, 9 μm

The following seal seam strength values were determined:

Sealing temperature 140° C.: no welding Sealing temperature 200° C.: nowelding

The damaging energy was 345 mJ.

The oxygen permeability was 20 cm³/m² dbars.

COMPARATIVE EXAMPLE 2

A five layer tubular film was produced as in Example 3, with theexception that the fifth layer (inner layer) consisted of purepolymamide 6/12, Grilon CF6S from EMS Chemie.

The following seal seam strength values were determined:

Sealing temperature 140° C.: 34 N/25 mm Sealing temperature 200° C.: 80N/25 mm

The damaging energy was 528 mJ.

The oxygen permeability was 6.0 cm³/m² dbars.

1. A five-layered, biaxially oriented, shrinkable, sealable tubular filmfor the packaging and wrapping of paste-like foodstuffs, meat, or meatwith bones, wherein the tubular film comprises: an inner layer comprisedof at least one copolyamide and a polymer material selected from thegroup consisting of at least one amorphous polyamide, at least onehomopolyamide, at least one modified polyolefin and mixtures thereof, alayer comprising a modified polyolefin, a middle layer comprised of apolymer material selected from the group consisting of at least onehomopolyamide, at least one copolyamide, at least one copolymer ofethylene and vinyl alcohol, a modified polyolefin and mixtures thereof,a layer comprised of at least one ethylene-vinyl alcohol copolymer, andan outer layer comprised of at least one polyolefin, at least onemodified polyolefin or a combination thereof.
 2. The tubular filmaccording to claim 1, wherein the inner layer comprises copolyamidesproduced from monomers selected from the group consisting ofcaprolactam, laurinlactam, ω-aminoundecanoic acid, adipic acid, azelaicacid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid,terephthalic acid, isophthalic acid, tetramethylenediamine,pentamethylenediamine, hexamethylenediamine, octamethylenediamine andxylylenediamine.
 3. The tubular film according to claim 2, wherein theinner layer comprises at least one copolyamide which is present in anamount ranging from 50 to 95 wt %.
 4. The tubular film according toclaim 1, wherein the inner layer comprises at least one amorphouspolyamide having a glass transition temperature ranging from 50 to 200°C. in a dry state.
 5. The tubular film according to claim 4, wherein theglass transition temperature of the amorphous polyamide ranges from 90to 160° C.
 6. The tubular film according to claim 1, wherein the innerlayer comprises homopolyamides produced from monomers selected from thegroup consisting of caprolactam, laurinlactam, ω-aminoundecanoic acid,adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid,dodecanedicarboxylic acid, terephthalic acid, isophthalic acid,tetramethylenediamine, pentamethylenediamine, hexamethylenediamine,octamethylenediamine and xylylenediamine.
 7. The tubular film accordingto claim 1, wherein the inner layers comprise at least one modifiedpolyolefin, which is a copolymer of ethylene or propylene and optionallyother linear α-olefins having from 3 to 8 C atoms and α,β-unsaturatedcarboxylic acids and/or metal salts and/or alkyl esters thereof, orgraft copolymers of the above mentioned monomers on polyolefins, orpartially saponified ethylene-vinyl acetate copolymers which areoptionally graft-polymerized with an α,β-unsaturated carboxylic acid andhave a low saponification level, or mixtures thereof.
 8. The tubularfilm according to claim 1, wherein each of the amorphous polyamide,homopolyamide and modified polyolefin in the inner layer, is present inamounts ranging from 0 to 30 wt % relative to the total weight of theinner layer.
 9. The tubular film according to claim 1, wherein the layeradjacent to the inner layer comprises a modified polyolefin or a mixtureof modified polyolefins.
 10. The tubular film according to claim 9,wherein the modified polyolefins are modified homo- or co-polymers ofethylene, propylene or combinations thereof and optionally other linearα-olefins having from 3 to 8 C atoms, which have monomers selected fromthe group consisting of α,β-unsaturated carboxylic acids or anhydrides,esters, amides or imides thereof grafted thereon.
 11. The tubular filmaccording to claim 9, wherein the modified polyolefins are copolymers ofethylene, propylene or combinations thereof and optionally other linearα-olefins having from 3 to 8 C atoms and α,β-unsaturated carboxylicacids, metal salts thereof, alkyl esters thereof or mixtures thereof, orgraft copolymers of the above-mentioned monomers on polyolefins, orpartially saponified ethylene-vinyl acetate copolymers which areoptionally graft-polymerized with an α,β-unsaturated carboxylic acid andhave a low saponification level, or mixtures thereof.
 12. The tubularfilm according to claim 1, wherein the middle layer comprises at leastone homopolyamide and/or at least one copolyamide produced from monomersselected from the group consisting of caprolactam, laurinlactam,ω-aminoundecanoic acid, adipic acid, azelaic acid, sebacic acid,decanedicarboxylic acid, dodecanedicarboxylic acid, terephthalic acid,isophthalic acid, tetramethylenediamine, pentamethylenediamine,hexamethylenediamine, octamethylenediamine and xylylenediamine.
 13. Thetubular film according to claim 12, wherein the middle layer furthercomprises at least one modified polyolefin produced by copolymerizationof ethylene or propylene and optionally other linear α-olefins havingfrom 3 to 8 C atoms and α,β-unsaturated carboxylic acids, metal saltsthereof, alkyl esters thereof or mixtures thereof, or graft copolymersof the above-mentioned monomers on polyolefins, or partially saponifiedethylene-vinyl acetate copolymers which are optionally graft-polymerizedwith an α,β-unsaturated carboxylic acid and have a low saponificationlevel, or mixtures thereof.
 14. The tubular film according to claim 12,wherein the middle layer further comprises a copolymer of ethylene vinylalcohol, and the amount of ethylene in the ethylene vinyl alcoholcopolymer ranges from 27 to 48 mole %.
 15. The tubular film according toclaim 12, wherein the amount of the modified polyolefin and/or theethylene vinyl alcohol copolymer ranges from 0 to 50 wt %, relative tothe total weight of the middle layer.
 16. The tubular film according toclaim 1, wherein a layer comprised of at least one ethylene-vinylalcohol copolymer is disposed between the middle layer and the outerlayer.
 17. The tubular film according to claim 16, wherein the amount ofethylene in said ethylene vinyl alcohol copolymer ranges from 27 to 48mole %.
 18. The tubular film according to claim 16, wherein the layerbetween the middle layer and outer layer further compriseshomopolyamides, copolyamides, modified polyolefins or mixtures thereof.19. The tubular film according to claim 18, wherein the homo- andcopolyamides are produced from monomers selected from the groupconsisting of caprolactam, laurinlactam, ω-aminoundecanoic acid, adipicacid, azelaic acid, sebacic acid, decanedicarboxylic acid,dodecanedicarboxylic acid, terephthalic acid, isophthalic acid,tetramethylenediamine, pentamethylenediamine, hexamethylenediamine,octamethylenediamine and xylylenediamine.
 20. The tubular film accordingto claim 18, wherein the modified polyolefins are produced byco-polymerization of ethylene or propylene and optionally other linearα-olefins having from 3 to 8 C atoms and α,β-unsaturated carboxylicacids, metal salts thereof, alkyl esters thereof or mixtures thereof, orgraft copolymers of the above-mentioned monomers on polyolefins, orpartially saponified ethylene-vinyl acetate copolymers which areoptionally graft-polymerized with an α,β-unsaturated carboxylic acid andhave a low saponification level, or mixtures thereof.
 21. The tubularfilm according to claim 18, wherein the amount of homopolyamide,copolyamide, modified polyolefin or mixtures thereof in the layerdisposed between the middle and outer layer ranges from 0 to 40 wt %,relative to the total weight of the layer.
 22. The tubular filmaccording to claim 1, wherein the outer layer comprises at least onepolyolefin, at least one modified polyolefin or mixtures thereof. 23.The tubular film according to claim 22, wherein the outer layercomprises at least one polyolefin selected from the group consisting oflinear low-density polyethylene, high density polyethylene,polypropylene homopolymers, poly-propylene block copolymers andpolypropylene random co-polymers.
 24. The tubular film according toclaim 22, wherein the outer layer comprises at least one modifiedpolyolefin produced by co-polymerization of ethylene or propylene andoptionally other linear α-olefins having from 3 to 8 C atoms andα,β-unsaturated carboxylic acids, metal salts thereof, alkyl estersthereof or mixtures thereof, or graft copolymers of the above-mentionedmonomers on polyolefins, or partially saponified ethylene-vinyl acetatecopolymers which are optionally graft-polymerized with anα,β-unsaturated carboxylic acid and have a low saponification level, ormixtures thereof.
 25. The tubular film according to claim 22, whereinthe modified polyolefins of the outer layer are modified homo- orco-polymers of ethylene, propylene or combinations thereof andoptionally other linear α-olefins having from 3 to 8 C atoms, which havemonomers selected from the group consisting of α,β-unsaturatedcarboxylic acids or anhydrides, esters, amides or imides thereof graftedthereon.
 26. The tubular film according to claim 1, wherein the tubularfilm comprises a coextruded and biaxially stretched tubular film whichhas been subjected to heat-setting.
 27. The tubular film according toclaim 1, wherein the wall thickness thereof ranges from 30 to 100 μm.28. A package for paste-like foodstuffs, meat, or meat with bonescomprising the tubular film according to claim
 1. 29. A bag comprisingthe tubular film according to claim 1 prepared by welding or sealing theinner layer on itself.
 30. Paste-like foodstuffs, meat, or meat withbones packaged in a bag according to claim
 29. 31. The tubular filmaccording to claim 7, wherein the α,β-unsaturated carboxylic acids areacrylic acid, methacrylic acid or combinations thereof.
 32. The tubularfilm according to claim 8, wherein each of the amorphous polyamide,homopolyamide and modified polyolefin in the inner layer, is present inamounts ranging from 5 to 25 wt %, relative to the total weight of theinner layer.
 33. The tubular film according to claim 10, wherein theα,β-unsaturated carboxylic acids are selected from the group consistingof maleic acid, fumaric acid, and itaconic acid.
 34. The tubular filmaccording to claim 11, wherein the α,β-unsaturated carboxylic acids areacrylic acid, methacrylic acid or mixtures thereof.
 35. The tubular filmaccording to claim 13, wherein the α,β-unsaturated carboxylic acids areacrylic acid, methacrylic acid or mixtures thereof.
 36. The tubular filmaccording to claim 14, wherein the amount of ethylene vinyl alcoholcopolymer ranges from 27 to 38 mole %.
 37. The tubular film according toclaim 17, wherein the amount of ethylene/vinyl alcohol copolymer rangesfrom 34 to 48 mole %.
 38. The tubular film according to claim 20,wherein the α,β-unsaturated carboxylic acids are acrylic acid,methacrylic acid or mixtures thereof.
 39. The tubular film according toclaim 24, wherein the α,β-unsaturated carboxylic acids are acrylic acid,methacrylic acid or mixtures thereof.
 40. The tubular film according toclaim 25, wherein the α,β-unsaturated carboxylic acids are selected fromthe group consisting of maleic acid, fumaric acid, and itaconic acid.41. The tubular film according to claim 1, wherein the wall thicknessthereof ranges from 40 to 80 μm.